Contains methods for reading in surface data file and determining
two-dimensional subgrid weights as well as writing out new surface
dataset. When reading in the surface dataset, determines array
which sets the PFT for each of the [maxpatch] patches and
array which sets the relative abundance of the PFT.
Also fills in the PFTs for vegetated portion of each grid cell.
Fractional areas for these points pertain to "vegetated"
area not to total grid area. Need to adjust them for fraction of grid
that is vegetated. Also fills in urban, lake, wetland, and glacier patches.